a) Field of the Invention
The present invention relates to control apparatus and method for an internal combustion engine and, more particularly, relates to intake air quantity controlling apparatus and method for the internal combustion engine which simultaneously control an opening angle of a throttle valve and a valve closure timing of an intake valve (each intake valve) according to an engine load condition.
b) Description of the Related Art
In an internal combustion engine in which an intake air quantity is controlled through a throttle valve, a loss in throttling around the throttle valve (called, a throttling loss) is involved and this causes a fuel consumption of the engine to be worsened.
To improve the fuel consumption, a variable valve driving apparatus has been proposed in which such a throttle valve as described above is eliminated and a valve closure timing of each intake valve is controlled so as to suck an appropriate quantity of intake air under the atmospheric pressure condition in an intake system of the engine, thus the intake air quantity control being controlled (refer to a Japanese Patent Application First Publication No. Heisei 8-246823 published on Sep. 24, 1996).
However, since no intake air negative pressure occurs in the intake system of the engine in such a variable valve driving apparatus as described in the BACKGROUND OF THE INVENTION having no throttle valve and the intake air quantity is regulated through the control over the closure timing of the intake valve(s), it is difficult to suck and process an EGR (Exhaust Gas Recirculation) gas, a purge of vaporized fuel from a canistor, a purge of a blow by gas within a crank casing into the intake system of the engine due to a presence in the intake air negative pressure.
It is therefore an object of the present invention to provide an intake air quantity control apparatus and method for an internal combustion engine in which valve closure timing of the intake valve(s) for each cylinder and an opening angle of the throttle valve (hereinafter also referred to as a throttle position of the throttle valve) are appropriately controlled so that an intake pressure having an appropriate magnitude is secured under a predetermined low engine load condition, the intake air quantity being controlled, so that a suction processing for the EGR gas, vaporized fuel, blow-bye gas, and so on utilizing the intake air negative pressure is carried out.
According to one aspect of the present invention, there is provided with a control apparatus for an internal combustion engine, comprising: a throttle valve installed in an intake system of the engine; at least one intake valve installed to open and close each corresponding combustion chamber of the engine; a throttle valve controller controlling a throttle position of the throttle valve in such a manner that an intake air negative pressure around the throttle valve is maintained constant at an approximately predetermined negative pressure value under a predetermined engine load condition; and an intake valve controller controlling a valve closure timing of the intake valve to regulate an intake air quantity supplied to the engine under the predetermined engine load condition.
According to another aspect of the present invention, there is provided with a method for controlling an intake air quantity of an internal combustion engine, comprising: controlling a throttle position of a throttle valve installed in an intake system of the engine in such a manner that an intake pressure around the throttle valve is maintained constant at an approximately predetermined negative pressure value under a predetermined engine load condition; and controlling a valve closure timing of at least one intake valve installed to open and close each corresponding combustion chamber of the engine to regulate an intake air quantity supplied to the engine under the predetermined engine load condition.
This summary of the invention does not necessarily describe all features so that the invention may also be a sub-combination of these described features.